Hydrology and suspended sediment
yield in Sungai Kinabatangan

Abstract

The quality of many rivers today is affected by anthropogenic factors such as land
use conversions and industrial developments. These activities have altered the
pattern of runoff, increased the sediment loads delivered into river channels, and
inadvertently affect the quality of river water. This study was carried out to (a)
analyse the hydrology characteristics of Sungai Kinabatangan Catchment; (b)
determine the sediment yield in the Sungai Kinabatangan Catchment; (c) develop
baseline hydro-geometry data of Sungai Kinabatangan and its tributaries; and (d)
design flow duration curves (FOC) for ungauged rivers in the Sungai Kinabatangan
Catchment. The four objectives were determined by field measurements of river
geometries as well as analysis of long-term gauging station data. For the first
objective, this study found that the Sungai Kinabatangan Catchment portrays
hydrologic characteristics of a large catchment. It is mainly dominated by baseflow
and less responsive to rainfall. The second objective determined that the sediment
yield in the Sungai Kinabatangan Catchment averages about 250 to 1,250
tonjkm2fyear. The amount is deemed tolerable and the yield has been relatively the
same since previous studies carried out 20 years ago. Hydro-geometry
measurements (width and depth of a channel) were obtained for 17 tributaries
within the Sungai Kinabatangan Catchment as well as the main river stem itself.
These measurements are useful in establishing a baseline of hydro-geometry data
for Sungai Kinabatangan. For the final objective, the design FOC for all the
tributaries in the Sg. Kinabatangan basin was established based on the data from
five existing gauging stations in the basin. Flow regime for each tributary could be
extracted from the design FOC. This method is useful in the estimation of flow for
small tributaries within a big catchment. It is especially practical where numerous
high-order streams drain into the catchment and these streams are less accessible
or are without a gauging record.